XVI International Botanical Congess

Actinorhizal nodules are modified lateral root organs containing the N-fixing actinomycete Frankia. We report our structural studies of a developmentally novel actinorhiza formed by plants in the genera Datisca and Coriaria. Unlike other actinorhizae, infected cells in Datisca and Coriaria progress through the cell cycle (become multinucleate) during development and the bacterial symbiotic vesicles (SVs) that differentiate become oriented en masse so that they all point toward the central vacuole of the infected cell. This hollow sphere of SVs is coated with a blanket of plant mitochondria. We are interested in understanding the cell biology of this complex development and will report our latest data addressing our hypothesis that infection stimulates cell cycling and the plant cytoskeleton orchestrates the arrangement of the SVs and mitochondria in these cells.